Both epidermis and mucosal epithelia are highly dependent on resident self-renewing stem cells, making them particularly vulnerable to physical and chemical insults compromising the repopulating capacity of the epithelial stem cell compartment. This is often the case in cancer patients receiving radiation or chemotherapy, many of whom develop mucositis, a debilitating condition involving painful and deep mucosal ulcerations as a result of damage to the normal tissue (Sonis, Oral Oncol., 45, 1015-1020 (2009); Sonis, Oral Diseases, 16, 597-600 (2010)). Mucositis causes distress to the patients and results also in substantial increase in per-patient care cost (Nonzee et al., Cancer 113, 1446-1452 (2008)). Radiotherapy is one of the most widely used cancer treatments (Begg et al., Nat. Rev. Cancer, 11, 239-253 (2011)), and although technical advances now allow a more targeted delivery of radiation to the cancer cells, indirect damage to the normal surrounding tissues still remains a common and frequently weakening side effect (Citrin et al., The Oncologist, 15, 360-371 (2010)). Hence, therapeutic interventions that can reduce the deleterious effects of chemotherapy or radiation on normal epithelial stem cells are needed that will improve on the quality of life of cancer patients and treatment outcome.